Apparatus for steering mineral mining machines



APPARATUS FOR STEERING MINERAL MINING MACHINES Filed Aug. 29,, 1963 J.DOWELL Nov. 7, 1967 MPU 3 Sheets-Sheet 1 I I I I I l l I I I I I n l I II I I I a I I I I I I r C v R CG C6 m u I m m n m W W m P m z u n. 5 5

PRI

FIG. I.

ATTORNEYS Nov. 7, 1967 .1. DOWELL 3,351,335

APPARATUS FOR STEERING MINERAL MINING MACHINES Filed Aug. 29, 1963 3Sheets-Sheet 2 MPU RAS cMc RC w.

CGI (:02 1

Nov. 7, 1967 J. DOWELL 3,351,385

APPARATUS FOR STEERING MINERAL MINING MACHINES Fi d g- 29 19 e sSheets-Shet s 34 i A 2 j///// v v; n A 4 a s a I L- J INVENTOR 2| aer NJOSEPH DOWELL ATTORNEYS United States Patent 3,351,385 APPARATUS FORSTEERING MINERAL MINING MACHINES Joseph Dowell, Coalville, England,assiguor to Coal Industry (Patents) Limited, London, England, a companyof Great Britain Filed Aug. 29, 1963, Ser. No. 305,400 Claims priority,application Great Britain, Sept. 4, 1962, 33,864/62 Claims. (Cl. 299-1)The present invention relates to apparatus of the kind utilizing theback-scatterng of electromagnetic radiation for steering a miningmachine in a seam of mineral so that the machine follows a desireddirection of travel with respect to the boundary of the seam. Apparatusof this kind has been proposed, and the present invention isparticularly directed to an improved automatic form of such apparatus.

According to one aspect of the invention, in a system for automaticallysteering a mineral mining machine with respect to the boundary of a seamof mineral including circuit means adapted to give an output responsiveto an amount of electromagnetic radiation back-scattered by materialadjacent to the machine, gating means are pro vided whereby said outputor a derivative thereof is only passed to further circuit means forspaced intervals in time, the latter circuit means being adapted toeffect control of the direction of travel of the machine. With thissystem, steering correction is only obtained at discrete intervals oftime or of distance along the path travelled by the machine in themineral.

According to a second aspect of the invention, apparatus forautomatically steering a mineral mining machine comprises an extensiblehydraulic jack for adjusting the direction of travel of the machine inthe mineral seam, a source of electromagnetic radiation, and atdetecting device responsive to the amount of radiation back-scattered bymaterial adjacent to the machine, the jack, source and device beingmounted on the machine, and further comprises a ratemeter circuitconnected to the detecting device and adapted to produce an outputsignal representative of the aforesaid amount of back-scatteredradiation, trigger means fed with the ratemeter output arranged tooperate valves controlling supply or exhaust of hydraulic fluid to orfrom the jack, and gating means adapted to pass the ratemeter output tothe trigger means only for discrete periods in time, whereby steeringcorrection is obtained only at discrete intervals of time or distancealong the path travelled by the machine in the mineral.

Preferably the gating means is arranged to pass the ratemeter output tothe trigger means at regular intervals.

Twospecific embodiments of the invention will now be described withreference to the accompanying drawings, in which:

FIGURE 1 is a diagrammatic representation of a first embodiment of asystem according to the invention for steering a longwall coal miningmachine of the trepanner type which rides on the floor of the coal seamadjacent to an armored face conveyor;

FIGURE 2 is a diagrammatic side elevation of a longwall coal miningmachine of the well-known drum or disc shearer type which rides on anarmored face conveyor,

FIGURE 3 is a diagrammatic representation of a second embodiment of asystem according to the invention for steering the machine shown inFIGURE 2,

FIG. 4 is a diagrammatic representation of a preferred form of distancesensing device for use in the systems shown in FIGS. 1 and 3, and FIG. 5is a section through pad 13 taken along line 55 of FIG. 1.

Referring to FIGURE 1, the mining machine (not shown) is steered in thevertical plane by means of a double-acting hydraulic ram or jack havinga cylinder Patented Nov. 7, 1967 11 rigidly secured to the machine bodyand a piston 12 rigidly secured to a support pad 13 which rides on thefloor of the mineral seam. The control of fluid supply and exhaust toand from the jack 10 is eliected by means of known electro-hydraulicvalves V1 and V2 which are themselves controlled as will be hereinafterdescribed. The precise construction of electro-hydraulic valves V1 andV2 forms no part of the present invention and can therefore be brieflydescribed. Each of V1 and V2 comprises a hydraulic valve controllingfluid flow to and from the jack, the valve member being coupled to thearmature of a solenoid. The valve is in the open condition when thesolenoid is energized by an electric current, and in the closedcondition when it is not. The hydraulic jack 10 is located just to therear of the trepanning cutter head at the forward end of the machine inthe normal position for such a machine, and pivots the machine about itsrear end riding on the seam floor.

A radioactive source 15, such as thulium 170, is encased in shielding 16and mounted in the underside of the jack 10. The source 15 is adjacentto a thick radiation shield 17, on the other side of which are arrangedthree parallel Geiger-Muller detector tubes 1%, 19 and 20, their axesbeing parallel to the direction of travel of the machine. Items 15-21are mounted in an insert in the underside of the support pad 13 so thatthe source 15 is disposed closely adjacent the strata underlying the-pad13 with the detectors adjacent the source and on the face side of it.For the sake of clarity, FIG. 5 shows items 15-21 on a larger scale. Inan alternative embodiment (not shown) there may be two Geiger-Mullerdetector tubes arranged one on each side of the source, shielding beinginterposed between each tube and the source, and the tubes beingparallel to the direction of travel of the machine. The casing includingthe source and the detector also includes, in a unit 21, atransistorized pro-amplifier for initial amplification of the signalfrom the detector tubes. The precise construction and electricalcircuitry of the pre-amplifier unit 21 form no part of the presentinvention and do not differ from the construction and circuitry alreadywell-known for pre-amplifiers for use in amplifying the signal fromknown Geiger-Muller detector tubes. The unit 21 is therefore notdescribed in detail. The parts 1021, V1, and V2 are all located on themining machine, but the remaining parts to be described may be locatedeither on the machine or in a main equipment console at a remote controlstation, for example at the end of the gate road in the mine. Theconnection between those parts of the system located on the machine andthose parts located at the end of the gate road is by means of extraelectrical conductors in the trailing cable attached to the machine andwhich normally serves to supply the electrical power for driving themachine cutting head. This connection is shown by dotted lines in FIGURE1.

The signal from the pro-amplifier 21 is fed to a ratemeter circuit R. Aswith unit 21, the circuitry of the ratemeter R is wholly conventional,and therefore will not be described. The mains power to energize theratemeter R is derived from a mains power unit MP'U, the details ofwhose circuit once again form no part of the novelty of the presentinvention. The output from the ratemeter R, which is representative ofthe amount of radiation backscattered by material adjacent to themachine and which varies according to the thickness of coal overlyingthe rock beneath the machine, is fed to a meter M and to a comparator C.The meter M gives a visual indication at a suitable control point at theend of the face or in the gate road of the thickness of coal beneath themachine. The comparator C is also fed with a signal derived from alinear potentiometer P attached to the piston 12 of the hydraulic jack.This potentiometer P is arranged to give an output voltage proportionalto the jack extension. The comparator C compares the ratemeter signaland the jack potentiometer signal and produces an output representativeof the steering correction required to restore the machine to a desireddirection of travel, and this output is fed to trigger means comprisingthe trigger units T1 and T2. Each of the trigger units T1 and T2comprises a monostable multivibrator circuit in conjunction with acoincidence gate stage and the manner of operation is such that when asignal arrives at the coincidence gate stages from the haulage samplingmeans S, to be described hereinafter, then the signal from thecomparator C, which is continuously fed to the units T1 and T2 isenabled to operate. Unit T1 is the low count trigger unit and respondsto signals of a low count rate which show that the coal thickness isless than desired (back-scattering by coal being greater than that by acorresponding thickness of rock). Unit T1 is arranged to give an outputfor a preset time after opening of the coincidence gate CG1 and thisoutput then opens valve V1 for the said preset time and thus initiates acorrespondingly predetermined extension of the jack 10, since apredetermined quantity of fluid flows into the jack when the valve V1 isopened for a preset time, causing the machine to cut upwardly and tendto return to the desired level. Unit T2 is the high count trigger unitand responds to signals which show that the coal thickness is greaterthan desired. Unit T2 then opens valve V2 for a preset time causing thejack to contract by a predetermined amount and the machine to cut down-'wardly.

Haulage sampling means S connected to the two units T1 and T2 acts tomodify the operation of T1 and T2 in such a way that when a signal isfed to either T1 or T2 by the means S at any instant, then theappropriate one of the coincidence gates are Opened and the appropriatevalve V1 or V2 is energized.

The haulage sampling means S and an associated sensing head D isincluded because the distance separating the radio-active source and thecutter of the mining machine makes it necessary to prevent a furtheroperation, once an operation of the steering mechanism has been made,until the source and detection equipment has determined the distancebetween the new floor level and the coal/ rock interface.

Referring now to FIG. 4 which shows a preferred form of distance sensinghead D, the necessary delay between each operation of the steeringmechanism is achieved by counting the teeth a on a sprocket 30 whichdrives the machines hauling chain, and permitting operation of thesteering mechanism (if required) only once for every eight or sixteen orother convenient number of teeth counted, i.e. at regular intervals ofdistance travelled by the machine.

The distance sensing head D is located adjacent to the teeth 30a of thesprocket driving the haulage chain by which the machine is pulled alongthe face. The distance sensing head D consists of a simple search coil31 whose reluctance is changed by the passage past it of each of thesprocket teeth 30a. The coil 31 is mounted in a strong case 32 andmoulded in loaded Araldite 33. The inductance of the coil is 2.1 mH, andthis is tuned to resonate at 5.5 kc./s by a capacitor 34 locatedadjacent the coil 31. The search coil 31 is fed from a 5.5 kc./soscillator 35 which is located in the console equipment. The search coil31 is provided with a gapped magnetic circuit 36, the coil being locatedso that the gap faces the teeth 30a of the sprocket which drives thecutting machines hauling chain. As each tooth 30a passes the gap a pulseis passed to the haulage sampling means S. The coil thus gives a pulseeach time a tooth passes and these pulses are received by register ordivider circuits of known construction which are arranged, in oneparticular example, to provide one output pulse for every sixteensprocket teeth.

It will be seen, therefore, that in operation of this system, the outputof the comparator C is only passed to the trigger means T1 and T2 atspaced intervals of distance along the path travelled by the machine.

A second embodiment of the present invention will now be described withreference to FIGURES 2 and 3.

Referring to FIGURE 2, the mineral mining machine, which in this exampleis a coal cutter-loader machine of the well-known drum shearer type, hasa body which rides on an armoured conveyor 111 and carries a cutter drum112 and a plough member 113. The body has sliders 114 and 115 which rideon the side frame members 116 of the conveyor and the plough member 113is attached to the slider 115 by a pin 113a. The vertical position ofthe body 110 and drum 112 can be altered by a double acting hydraulicram or jack comprising a cylinder I, piston P and piston rods PR1 andPR2. The rods PR1 and PR2 act on a frame member F attached to slider 115and the cylinder J is rigidly attached to the body 110. A v-ray source(RAS in FIGURE 3), e.g. thulium 170, and detector means (GMC in FIGURE3), e.g. a Geiger-Muller counter, are mounted in the bottom of theplough 113 in protective containers 118 and 119 respectively positionedwith the source roughly centrally across its width and towards the endof the plough nearer to the cutter drum 112, and with the detector meansadjacent to the source and on the face side of it. An interlock isfitted so that the plough 113 cannot be disconnected from the machinebody without the 'y-ray source being made safe.

Referring now to FIGURE 3, the output from the detector means GMC is fedto a pro-amplifier PA similar to unit 21 shown in FIGURE 1 and theoutput from the preamplifier is fed to a ratemeter R located in a mainequipment console, the latter being conveniently situated at the end ofthe main gate road serving the longwall face being mined by the machine.Connections from this console to equipment such as the mining machineand to the distance sensing head adjacent to the haulage sprocket areshown by dotted lines in FIGURE 3. The ratemeter R is conventional incircuitry and therefore is not described in detail.

As with the system shown in FIGURE 1, the ratemeter output is passed toa meter M, and also to coincidence gate stages shown as CG1 and CG2, oneassociated with each of two trigger units T1 and T2, these two unitsconstituting the further circuit means hereinbefore referred to. Asbefore, a mains power unit MPU supplies a stabilized +12 volts supply at350 ma. to the ratemeter and to the other circuits to be shortlydescribed. The ratemeter accepts the pulses from the pre-amplifier PAand integrates them to provide a DC output voltage which is proportionalto the input count rate. A pulse-lengthening circuit and various valuesof integrating capacitor (selected by means of a switch) are included inthe ratemeter circuit in order to provide compensation for variationscaused by decay of the radioactive source RAS.

The trigger units T1 and T2 control the operation of theelectro-hydraulic valves V1 and V2 respectively. Both the DC. outputfrom the ratemeter R and gating pulses from a part of the gating meansto be described are fed to the coincidence gate stages CG1 and CG2, and,providing a gating pulse is present coincident with a DC. output fromthe ratemeter above a preset maximum level or below a pre-set minimumlevel, either trigger unit T1 or T2 respectively will operate. As withthe system described with reference to FIGURE 1, operation of triggerunit T1 effects energization of the solenoid or valve V1 for a givenperiod, permitting a predetermined quantity of fluid to flow into thejack cylinder, causing the machine to tend to cut upwardly, whileoperation of unit T2 energizes the solenoid of valve V2 for a givenperiod, causing the machine to cut downwardly.

The gating means herein referred to comprises coincidence gate stagesCG1 and CG2 and the remaining parts (i.e. RC, SS, GPD, D and O,optionally plus T) now to be described which serve to generate pulses. Adistance sensing head D, identical to that described with reference toFIGURE 4 supplies one pulse per tooth of the haulage sprocket whichpasses a search coil, as previously described. The haulage sprocket willbe located on the cutter loader machine if a conventional drum shearerhaulage is employed, but it will be appreciated that the presentinvention is equally applicable to a machine moved along the face by aremote haulage at the face end, in which case the sensing head D will belocated at the haulage at the face end. The pulses are passed to agating pulse detector GPD which detects and re-forms them. The reformedpulses are then fed to the register circuit RC via a selector switch SS.The register circuit RC comprises a number of bistable dividers whichare located on a pair of printed circuit boards, and serves to dividethe number of pulses from sensing head D by a convenient number such as4, 8, or 16, so that the register circuit RC only gives one output pulseper 4, 8 or 16 teeth of the haulage sprocket which pass the head. Theoscillator 0 provides an output for driving the distance sensing head D.A second oscillator, not shown, is provided for controlling atime-gating circuit T which is an optional, though preferred, componentof the gating means. Selector switch SS permits selection of eithertime-gating or distance-gating, that is to say, either the ratemeteroutput causes operation of the appropriate trigger means at regularintervals of distance travelled by the machine along the face if switchSS connects register circuit RC to gating pulse detector GPD, or theratemeter output causes operation of the appropriate trigger means atregular (though adjustable) intervals of time if switch SS is in theother (lower in FIGURE 3) position. The detailed circuitry employed forthe stages RC, GPD, T and O has not been described as appropriatecircuits will be well within the knowledge of one skilled in theelectronics art.

Returnin now to the trigger units T1 and T2, these receive a signal fromthe coincidence gate stages CGl or CG2 respectively dependent upon thelevel of the DC. output from the ratemeter R and the presence of agating pulse from register circuit RC. If the ratemeter D.C. outputexceeds a preset reference level and assuming that a gating pulse fromregister circuit RC is present, trigger unit T2 will receive a pulsefrom coincidence gate stage CGZ and will operate and produce a pulse.This pulse is used to operate valve V2 for a time determined by thewidth of the pulse. This width is variable by an adjustable and manuallypre-set potentiometer (not shown). Similarly if the DC. output from theratemeter R falls below a pre-set reference level (again assuming thatthe gating pulse is present), trigger unit T1 will operate and effectenergization of valve V1 for a time governed by the width of the pulse.The levels of ratemeter output (corresponding to thickness of coal) atwhich the trigger circuits are operated may be pre-set by manualadjustment of variable potentiometers (not shown), one associated witheach of the trigger units T1 and T2.

The trigger circuits T1 and T2 are divided between two printed circuitboards, one board (T1) being associated with the Raise solenoid valveV1, and the other with the Lower solenoid valve V2.

It will thus be seen that in operation of the machine, when theback-scattered radiation received by detector GMC indicates that thethickness of coal overlying the rock or shale is a certain value, then aratemeter output of a certain DtC. level will reach coincidence gatestages CGl and CG2. If this level is less than the predetermined valueset in stage CGl, which will be when the coal thickness is less thanthat desired, then unit T1 will effect operation of valve V1, thuspassing a given amount of fluid and moving the jack piston P a givenamount in the direction (downwardly in FIGURE 3) which makes the machinecut upwardly. The next gating pulse will then permit the resultant ofthe continuous comparison of the ratemeter output and the preset levelsto be passed to the appropriate one of the units T1 and T2 and if thelevel of ratemeter output is still below that corresponding to thedesired coal thickness, then the valve V1 will again be opened and thepiston P again shifted by the given amount in the same direction; thusan intermittent, but repeated adjustment of the machine position ismade, the machine being allowed to cut for a certain distance (or timeif switch SS is closed to T) before further steering control is applied.In the practical application of this form of automatic steering, it hasbeen found very important that the machine should be allowed to cut fora short period when further control is not applied, in order to avoiddifficulties or" over-control and excessive hunting.

1 claim:

I. A system for automatically steering a mineral mining machine withrespect to the boundary of a seam of mineral using back-scattering ofgamma ray, X-ray, bremsstrahlung radiation and the like, comprisingfirst circuit means adapted to give an output in response to the amountof back-scattered radiation received by a detector on the machine,gating means adapted to pass said output when it is in error, namely,outside a given desired range, to a second circuit means adapted tocontrol in response to said output the direction of travel of themachine relative to the boundary of the seam, said gating meansincluding a distance sensing device adapted to sense movement of themachine along a mineral face and to produce in response to such movementa distance signal at spaced intervals of time corresponding to givenincremental distances traveled by the machine along the mineral face,said gating means being further adapted. to pass said output errorsignal to said second circuit means only if said distance signal issimultaneously present at said gating means.

2. A system as claimed in claim 1 wherein said distance sensing devicecomprises search coil means adapted to produce pulses in response topassage of the teeth of a chain sprocket wheel the rotation of whichcorresponds to linear movement of the mining machine along the mineralface.

3. Apparatus for automatically steering a mineral mining machinecomprising: an extensible hydraulic jack connected to the machine foradjusting the direction of travel of the machine with respect to theboundary of a mineral seam; a source of electromagnetic radiation and adetecting device responsive to the amount of radiation back scattered bymaterial adjacent to the machine, said source and said detector devicebeing mounted on the machine and being spaced apart a predetermineddistance by a shielding material mounted on the machine; a ratemetercircuit connected to the detecting device and adapted to produce anoutput signal representative of the aforesaid amount of back-scatteredradiation; trigger means connected to the said ratemeter circuit andarranged to operate a valve controlling fluid supply to said jack inresponse to said output signal when it is outside a given desired rangeforming an error signal; a gating crcuit connected to said trigger meansand including a distance sensing device adapted to sense movement of themachine along a mineral face and to produce in response to such movementa distance signal at spaced intervals of time corresponding to giveincremental distances traveled by the machine along said mineral face,said gating means being adapted to pass the ratemeter output to saidtrigger means only when the distance signal is simultaneously present atsaid gating means.

4. Apparatus as claimed in claim 3, including two trigger meansconnected to said ratemeter circuit, a first trigger means being adaptedto operate a first hydraulic valve only when the ratemeter outputexceeds .a given level and a second trigger means adapted to operate asecond hydraulic valve only when the ratemeter output is less than asecond given level, said first and second hydraulic valves beingoperable to control fluid supply to different sides 7 8 of adouble-acting hydraulic jack connected to the mining References Citedmachine for adjusting the direction of travel of the ma- UNITED STATESPATENTS chine with respect to the boundary of a mineral seam.

5. Apparatus as claimed in claim 4 wherein said dis- 3'019338 1/1962Monaghan et 2991 X tance sensing device comprises search coil meansadapted 5 3198580 8/1965 Eberle 299'1 to produce pulses in response topassage of the teeth of FOREIGN PATENTS a chain sprocket wheel therotation of which corresponds 857,251 12/1960 Great Britain to linearmovement of the mining machine along the mineral face. ERNEST R. PURSER,Primary Examiner.

1. A SYSTEM FOR AUTOMATICALLY STEERING A MINERAL MINING MACHINE WITHRESPECT TO THE BOUNDARY OF A SEAM OF MINERAL USING BACK-SCATTERING OFGAMMA RAY, X-RAY, BREMSSTRAHLUNG RADIATION AND THE LIKE, COMPRISINGFIRST CIRCUIT MEANS ADAPTED TO GIVE AN OUTPUT IN RESPONSE TO THE AMOUNTOF BACK-SCATTERED RADIATION RECEIVED BY A DETECTOR ON THE MACHINE,GATING MEANS ADAPTED TO PASS SAID OUTPUT WHEN IT IS IN ERROR, NAMELY,OUTSIDE A GIVEN DESIRED RANGE, TO A SECOND CIRCUIT MEANS ADAPTED TOCONTROL IN RESPONSE TO SAID OUTPUT THE DIRECTION OF TRAVEL OF THEMACHINE RELATIVE TO THE BOUNDARY OF THE SEAM, SAID GATING MEANSINCLUDING A DISTANCE SENSING DEVICE ADAPTED TO SENSE MOVE-